EFFECT OF SLAG COMPOSITION ON THE KINETICS OF THE REDUCTION OF IRON-OXIDE IN MOLTEN SLAG BY GRAPHITE

A kinetic study has been made on the reduction of iron oxide in molten slag with graphite. The composition of the primary slag was changed so that SiO2 concentration varied between 0.33 and 0.50 mole fraction, and slag basicity between 1 and 2. The experimental temperature was 1 300-degrees-C. The reaction rate is significantly affected by the slag composition. From values of the mass transfer coefficient, calculated by using penetration theory, it is presumed that for the slags with basicity of 2, the reaction rate is controlled by mass transfer in the slag phase, but chemical reaction resistance is predominant in slags with lower basicities. By applying a mixed-control model to the latter case, the apparent chemical reaction rate constant was calculated. The rate constant decreases largely with increasing the silica activity. The reaction rate also decreases with the presence of phosphorus in the slag. These behaviors indicate that the reaction rate is very sensitive to the interfacial chemisorption of the surface active agents.